This invention pertains to a dry cleaning system utilizing densified carbon dioxide and a surfactant adjunct.
Densified, particularly supercritical fluid, carbon dioxide has been suggested as an alternative to halo-carbon solvents used in conventional dry cleaning. For example, a dry cleaning system in which chilled liquid carbon dioxide is used to extract soils from fabrics is described in U.S. Pat. No. 2,012,194 issued to Maffei on Mar. 15, 1977.
Densified carbon dioxide provides a nontoxic, inexpensive, recyclable and environmentally acceptable solvent to remove soils in the dry cleaning process. The supercritical carbon dioxide has been shown to be effective in removing nonpolar stains such as motor oil, when combined with a viscous cleaning solvent particularly mineral oil or petrolatum as described in U.S. Ser. No. 715,299, filed Jun. 14, 1991, assigned to The Clorox Company and corresponding to EP 518,853. Supercritical fluid carbon dioxide has been combined with other components, such as a source of hydrogen peroxide and an organic bleach activator as described in U.S. Ser. No. 754,809, filed Sep. 4, 1991 and owned by The Clorox Company, corresponding to EP 530,949.
A system of dry cleaning fabrics using liquid carbon dioxide under stirring and optionally including conventional detergent surfactants and solvents is described in U.S. Pat. No. 5,467,492 corresponding to JP 08052297 owned by Hughes Aircraft Co.
The solvent power of densified carbon dioxide is low relative to ordinary liquid solvents and the carbon dioxide solvent alone is less effective on hydrophilic stains such as grape juice, coffee and tea and on compound hydrophobic stains such as lipstick and red candle wax, unless surfactants and solvent modifiers are added.
A cleaning system combining particular anionic or nonionic surface active agents with supercritical fluid CO2 is described in DE 39 04 514 A1 published Aug. 23, 1990. These anionic and nonionic agents, such as alkylenebenzene sulfates and sulfonates, ethoxylated alkylene phenols and ethoxylated fatty alcohols were particularly effective when combined with a relatively large amount of water (greater than or equal to 4%). The patented system appears to combine the detergency mechanism of conventional agents with the solvent power of supercritical fluid carbon dioxide.
It has been observed that most commercially available surfactants have little solubility in supercritical fluid carbon dioxide as described in Consani, K. A., J. Sup. Fluids, 1990 (3), pages 51-65. Moreover, it has been observed that surfactants soluble in supercritical fluid carbon dioxide become insoluble upon the addition of water. No evidence for the formation of water-containing reversed micelles with the surfactants was found. Consani supra.
Thus, the dry cleaning systems known in the art have merely combined cleaning agents with various viscosities and polarities with supercritical fluid CO2 generally with high amounts of water as a cosolvent. The actives clean soils as in conventional washing without any synergistic effect with the CO2 solvent.
The formation of water-containing reversed micelles is believed to be critical for the solubility and removal of hydrophilic stains. Studies of the interaction of surfactants in supercritical carbon double with water, cosurfactants and cosolvents led to the conclusion that most commercially available surfactants are not designed for the formation of reversed micelles in supercritical carbon dioxide as described in McFann. G., Dissertation, University of Texas at Austin, pp. 216-306, 1993.
The present invention provides an improved dry cleaning system utilizing densified carbon dioxide to clean a variety of consumer soils on fabrics.
The present invention provides a dry cleaning system utilizing an environmentally safe, nonpolar solvent such as densified carbon dioxide preferably in combination with a specified amount of a modifier, preferably water to effectively remove a variety of soils on fabrics. Particular surfactants useful in the drycleaning system are also described.
In one aspect of the present invention, the dry cleaning used for cleaning a variety of soiled fabrics comprises densified carbon dioxide and about 0.001% to about 5% of a surfactant. The surfactant has a densified CO2-philic functional moiety connected to a densified CO2-phobic functional moiety. Preferred CO2-philic moieties of the surfactant include halocarbons such as fluorocarbons, chlorocarbons and mixed fluorochlorocarbons, polysiloxanes, and branched polyalkyleneene oxides. The CO2-phobic groups for the surfactant contain preferably polyalkeneene oxides, carboxylates. C1-30 alkylene sulfonates, carbohydrates, glycerates, phosphates, sulfates and C1-30 hydrocarbons.
The dry cleaning system preferably contains a specific amount of a modifier, such as water, or an organic solvent. Optionally a bleaching agent such as a peracid is also included.
A method for dry cleaning a variety of soiled fabrics is also described wherein a selected surfactant, and a modifier, and optionally a bleaching agent or mixtures thereof are combined and the cloth is contacted with the mixture. Densified carbon dioxide is introduced into a cleaning vessel which is then pressurized from about 14.7 psi to about 10,000 psi the temperature is adjusted to a range of about xe2x88x9278.5xc2x0 C. to about 100xc2x0 C. Fresh densified carbon dioxide may be used to flush the cleaning vessel.